Picture processing includes a variety of algorithms employed at different stages within a recognition process. Although single parallel algorithms have been suggested, no systematic comparison with sequential algorithms is available. We propose here some parallel algorithms solving a selected set of picture-processing tasks and compare their speed, when implemented on a CLIP machine, with that of the equivalent sequential algorithms implemented on a standard minicomputer. It is shown that parallel algorithms are faster than the sequential ones by a factor depending on the size of the digitization matrix, even when arithmetical operations are widely involved.